Electromagnetic scanning system



p 1951 c. E. ToRscH METAL 2,568,471

ELECTROMAGNETIC SCANNING SYSTEM Filed NOV. 10. 1949 2 Sheets-Sheet 1LOAD j I j,

Inventors Charles EToT-sch, John B.Coullard,

bym,

p 18, 5 c. E. TORSCH ETAL 2,568,471

ELECTROMAGNETIC SCANNING SYSTEM Filed Nov. 10, 1949 2 Sheets-Sheet 2Fig.4.

TRANSFORMER CORE FLUX 0R SCAN/WW6 CURRENT TRANSFORMER cons FLUX 0RSCANNING CURRENT TIME I n vehtor" s Charles IiTorsch,

John B c oullai d,

The i r Attorney.

Patented Sept. 18, 1951 2,568,471 ELEoTRoMA NErIo soANNrNG SYSTEM Ch res. T 1 9 and hn (29 112.11 No th;

" r cu e, N- 5" ass n rsj. G.

ria Emmy c iim n a orn re QEk Application November 10, 19.49, Serial-No126,630.

7 Claims. (Cl. 3 .51137).

Ou nven i n relates to elec omag e sc y: nine ystems, and mo parti ulary o eleotro-t ma neti stems. of h ype. whic emp oy weep output ansformercon ctin a dri e uleewith a scan in inducta ce- In su h s: tems, theelectron scanning beam of the cathode ayube s. elec rornaenetisalldeflec ed c ica lsi-to effect; h eprqd ismoi animaee. ItiS a prima yobject. of o mention to i ease the iectroma ne ie scannin owe f i ncy ofsuc a sys em. w th a iven ume of r n ermer ore. ma r lilecirom gnetic sann nesy iems t h abo ype frequen ly a power. u put. d v c wh ch s. conncted to upply cyclica y varyin urre t hrough. a. sweep out utir nst mert a. c nnin n ietance hifi fil llpllllds e neck i-thel athode ay v ewi gdevic It k wn n such scanning systems to employ a damping tube which isconn cted; across. the ee nda y oi th p. o put; transfo mer a d whichmay be t wzed o provi e. a powe feedback r uit. o he were ou put ube:Sueh. Powe e back. s stem o example, di c es d. S- Bateni 2-,$ 1,6 .l,ranted October 9, 3. t G- E Hirsch, In such an .nsemeni the ma e icsweep ene y eseumul edadurinehelatter ha f i thet ae interval. and toredn he scannin in uctan durin the retrace per ds f th eemin eam a ses-a.current flow throu the dam e ube ur n the. nitial por ion of. the ubseqnt ss nning peried; If. he da p tu e and dr ve u cure tsare p rox matelyqu the ue e ices e. cross. conne ted s as to ob a. power feedback efie twith c nsequent .,.e e n. the emcie ev o the. ste The ..inR ime r ent sombined with th cur ent Quip ii, of the owe tube o effect u stantia lyiiieeibe m t m i pcii. the. cat ode ray tube. wen: uch. rr n em nts deal uti i a. swizenireps pimer wh eiiife ste do atio Qf: approximately 1 5t is opti un and wlerein iie -i ii eii q ei een f. rimar a d; s qiii eseiicie i ii i eeei me equal so as to jzw iiip e he. ne -rim .iq ed. r sn i9?!- We havefcund. that such systems do not make full use of thecapabilities of the core materialin thesvveep t ansfprmell 6 to the factthat a. flux biasing effect is produced. in the trans-i tgor mer core asa result of an. unbalance in the primary and, secon magnetizing forceset up. in the transfo core. The flux biasing efiect au s h E P- 8 991of h traniformer 99 2 s iii iir ii substan i l. moun whiih 1 2 ea s at as bstan l cr se vin power must. be supplied to. obtain th desired 'qggfle ion t he q re e m in t e i s i. core saturation. 'Ifhe. BH curves ofmany "core mater l eme Q d n. weep s oi e S h as, for example, theferrite magnetic core in terial disclosed in the copending application01; E. Torsch, Serial No. 95352, which wasflled on May 2 7 19 49 and isassigned to, thei'sa ne assignee as the present invention, are of. thesteep slope variety and henceare. sensitive to relative 1y. mal com onens i ne'i-D-c. cor m n m: on, T a o e-de ei d-r str i o 2 e fluxexcursion relative to negativefiux excurs q for balanced-magnetizingforce excursionslresuits in an appreciable compression of the right-handpic ur el me t a d deii n ei Q h ip p e raster vertical edges toward thelei-t-handsi oi o he emen, T isco di n. is ar-i ar ras: pare t- W en hvo m 9i q re a s in d cedo a enomi m m or t 9 o en revr qu d 9 i edhe iim nd c ance.

we; h e ou d; t un e able o sa ira r n effe ts experie c d in c n e t lc s): ma n c deflection iems ey be b tan iall lim nate ntrodu i a c mens ting? rent.- n t e rensiqrm r which e e o. shift the o atin i t o hen fo me e. s! a more. symm ir eal. os t n on h H: cum? thereof.-Accordingly, it is an object of our. in.- eiiiion 0 erev sie n w a d rve el q rq magnetic scanning system in which substantially nc ea e efiien y t d.-

It is another objectof ourinvention to provide a new and im ro ed el tom c g system wherein. a; sweep. transformer having a re ative y smaliolume of; o m te l y.- b employed without sacrificing a previouslyestab.- i ed le el: o owe t n fe efiiciency- Itfis a further object ofour invention to pro: is e an mp o e e trom e .95%? ine y ie -i wh ch. asweep iransi e having ive vo ume Q or mater l s abl to p oduce ub tantal nc ased m t i iii qiniis: n c defleqt e en rgy- Brieii i epce a wwith our nveni cn he operating. point of the sweep. output transformershifted. by. meansof an auxiliary unidirectional re i which pa s dthrough. a nd n ii thesweepftransformer. in the proper direction toprovide, suificien additional magnetizing for e tobalance theunidirectional component one neti rig force set by" the flow of. our

In a. preferred through the primary. W1 d1 g,

i iib l ineiitsu i au i iar rr n s i -evi Qii.

through a shunt connected width control thereby producing relativelylittle displacement of the picture for the same change in linearity ofthe scanning wave form as would be produced by direct connection to thesweep yoke. Raster decentering may be independently accomplished bywell-known auxiliary magnetic means such as focus coil tilt and/ordisplacement, or centering ring magnets.

The features of our invention which we believe to be novel are set forthwith particularlity in the appended claims. Our invention itself,however, both as to its organization and method of operation, togetherwith further objects and advantages thereof, may best be understood byreference to the following description taken in connection with theaccompanying drawing, in which Fig. 1 is a schematic diagram of anelectromagnetic deflection circuit embodying the principles of ourinvention; Fig. 2 is a schematic diaa gram of an electromagneticdeflection circuit embodying the principles of our invention inalternative form; Fig. 3 is a characteristic curve for a portion of theapparatus of Fig. 1, used to illustrate the operation thereof; and Figs.4 and 5 are waveforms for a portion of the circuit of Fi 1.

Referring now more particularly to Fig. 1 of the drawing, there isillustrated therein a power output tube I, which is used to control theflow of sweep energy through a sweep output transformer 2. The sweeptransformer 2 is connected to the coils of a scanning inductance 3 whichmay be in the form of a conventional scanning yoke which surrounds theneck of a cathode ray tube and operates electromagnetically to deflectthe electron beam of the cathode ray tube. A voltage wave of the desiredsawtooth shape is applied through a capacitor 4 to the control electrode5 of device I. The cathode 6 of device I is connected to ground and theanode I of device I is connected to one end of primary winding 3 ofsweep transformer 2. The other end of primary winding 8 is connected toa. capacitor I and inductance II. The screen electrode 9 of device Iisenergized by a separate source of unidirectional potential under thecondition of operation shown in Fig. 1. Inductance II is preferably madevariable by means of a conventional tuning slug of powdered iron,ferrite magnetic material, or the like. The other end of inductance IIis connected to a capacitor I2, capacitors II! and I2 also beingconnected to ground. A grid leak resistor I3 is used to complete thecontrol electrode path of device I. One end of the secondary I of sweepoutput transformer 2 is connected to the anode I6 of an electrondischarge device I! of the diode type. The cathode I8 of device I I isconnected to the junction point of inductance II and capacitor I2. Thesecondary winding I5 is also connected to an auxiliary isolatinginductance 26, which may be constituted as a width control inductancepreferably made variable by means of a movable core of powdered iron,ferrite magnetic material, or the like, the other end of D.-C. loadisolating inductance being connected through a capacitor '2I to theother end of secondary winding I5. A variable resistor 26 is connectedacross capacitor 2I, this resistor being used to control the flow ofcurrent through secondary I5 in a manner to be described more fullyhereinafter. A blocking capacitor 22 is used to connect the lower end ofthe scanning inductance 3 to the lower end of secondary winding I5.Anode potential for device I is supplied by a unidirectional source ofsupply indicated by the battery 25, the positive terminal of which isconnected to the lower end of secondary winding I5.

Considering now the operation'of the abovedescribed electromagneticdeflection system, a sawtooth scanning waveform is supplied to thecontrol electrode 5 of device I and operates to control the flow ofcurrent therethrough so as to produce in the primary winding '8 acurrent of substantially sawtooth shape. However, due to the operationof the damping tube H, the current through primary winding 8 issubstantially class B, that is, no current flows in the winding duringapproximately the first third of the picture trace interval. During thebalance of the trace a plate current of triangular shape rises to a peakof about three times the average or unidirectional component thereof.Likewise the secondary current waveform is substantially class B,beginning with a peak current at the initiation of the picture trace anddecreasing to zero near the center of the trace. The magnetizing forcein the core produced by the unidirectional component of the primarycurrent tends to allow saturation of the core during peak currentintervals.

Due to the action of the damper tube IT, a unidirectional component ofsecondary current is established, which unidirectional component isutilized in the power feedback system shown to in crease the over-allcircuit efficiency. Thus, energizing potential for device I is suppliedthrough battery 25 and the secondary winding I5, through the dampingtube and isolating inductance II to the high potential end of primarywinding 8. By such an arrangement, the unidirectional component producedby the damping tube is added to the battery potential for energizationof device I.

Inasmuch as the unidirectional component of current which flows throughsecondary winding I'5 due to the damper and yoke load is, by feedbackconnection, the same as the rectified component of anode current whichflows through primary winding 8, it would appear that the magnetizingforce produced by the flow of current through windings 8 and I5 would beequal and therefore the net magnetic force due to the unidirectionalcomponents of the currents would be equal and hence the operating pointof the transformer would be symmetrically positioned on the B/ H curveof the transformer core material. However, due to the core and copperlosses in the scanning inductance 3, driver tube I and isolatinginductance 20, and due to leakage reactance, core and copper lossesWithin the transformer itself, a stepdown ratio between primary winding8 and secondary winding I5 of approximately 1.5 to 1 has been foundoptimum for highest efiiciency and best cathode ray trace linearity withsubstantially unidirectional feedback of secondary damping energy to theprimary.

With such a stepdown ratio, the ampere turns, and hence the magnetizingforces produced by the two windings, are unequal, the primary ampereturns being substantially greater than the secondary ampere turns. Thismeans that the magnetizing force produced by the primary current issubstantially greater than the secondary magnetizing force and there isproduced in the core material a constant unidirectional magnetizingforce which biases the operating point of the transformer away from thegeometric center of the family of B/H curves of the core material. Thenet effect of this magnetic bias is to offset the utilize astepdownratiohetween,primaryandssew .pndany .Windingscifa-sufdcientvalueto give .un- .balance .in primary and .secondary magne tiZing forces,there is illustrated in Fig.3 a'typicaIB/H icunvenf .thecoremateriallofaconventionalsweep .nutpu-t transformer. In Fig. 13, 'the generalizedFB/H .curve of the core..material is illustrated by .the curve-.30,which under staticconditions'starts at .theintersection o"f .thefBandIHaxes. Due 'to theabore-clescr'ihed .flux biasing .effect, j the ODer-.ating pointis shifted by an amount "AH'.to.a'newpositionvillustratedias 'With the new oper- .a'.i'.in g ,point O.asa.center,the core'is now sub- .j ected .to egual magnetizing iforces-AHR and AI-Ir. which correspond respectively to deflection ofthe...ca,tho,de ray beam .to .the right-hand andlefthand edges ofthescreen and which .causecorresponding iflux .variations .ABR and .ABLrespectively. 'TheseQflux variations ABR and ABL are reflected-ascorresponding deflections ,o'f the catnode :ray beam .to .the -righthand andle'ft-hand .edges .of .the screen respectively. .However, it

apparent Irom .an inspection .of Fig. 3 that the flux excursions ,ABR.and 'ABL are not equal .although they are .producedjfrom identicalmagnetizing force excursions A'Hnand 2XHL,I1116"IO the saturationeffects .of 'thecore. iIhus, to obtain .a linear output the coremustbegreatly .overdriven .or else the output or the transformer mustbeseverely limited for a given volume of core ma- 'terial.

To illustrate further the efiects ofcoresatnration on'the shape of theoutput wave ofthe defiection system, we haveshownin Fig. 4 atim'ingwaveform of the current produced in the scanning inductance 3ofFig. "1.This'wave'form also illustrates *the' variations in transformer coreflux density B and may be used'to -correlafte thedeflecti'on of thecathode "ray beam-and the trans- *formeroperatingcharacteristic.

-Referring *to Fig.4, the sawtooth-wave-*of-scancling-current 31 isflattened in theregion of transformer core saturation :32 which resultsinan-un desirable compression of the right-hand picture elements on theraster. Also, =due to the-unequal dehec'tionsabout the *biasedoperating=point which also corresponds to :the undfiected spot positionon the-nathode-ray tube screen,-the-edges of the raster 32 ared'ecenteredftowardthe left- :liand -edge of -the screen. This is at onceevident from -a consideration of the neutral transformer core position'0, illustrated :by fithe sd'otted line 33, which is spaced below theactualaoperating point 0 by 'the'amount-cif the eore fiu-x' biasandwhich would ideally correspond -.to the undeiflected spot position.

In accordance with our invention, zansauxiliary unidirectional currentis passed 'through the-seo 'ondary winding in theproper directionto.create a new magnetizingforce which oppcses theihiasring force -AH =0'fFig. :3 and shifts wthe :operating 275 in thereircuitzof :pointatmamoreesymmetrical POSitiOmaS the :B {H ieurrei 33575511011anarrangementsassubstantially cgreateradefiectioniispermitted-beforelthetcoredcecomes saturated. .ii-heaeffectaof operationof :the transformencore ;at :its :neutral flux position Oziseil'lustrated in Fig. r5- wherein the scanningxcurren't waveform ithusobtained is shown. In. Fig. 15, it ZiS'iGViClBIlt JEhat [the scanningwaveform $34 .undergoes-equal excusions :Di and-Dzfrom the neutralpositionfl, which position also corresponds to'ithe :undeflectedposition :of :the :cathode .ray :sbeam. tThe amplitude of wave :34 isincreased duez-tothe operation of :the transformer -.in an unsaturatedregion :gand linearity is substantially improved oyer that :of Fig. '4..-Also, no crowding :of :the right-ihandypicture elementsis producedwith the symmetricalsscanningwaveof Fig. 5.

ilnwthercircuit of Fig.;,1, the compensating .comiponentzof secondaryicurrent: necessary to obtain :unbiased -.tr-ansformer =.coreoperationis produced Joy :connectingran :auxiliary load circuit tothe junction.point of: shunt width control "-26 and-"ca- .pa'citor 21. The-auxiliaryload-maycomprise any npowerzconsumingtcircuit in thereceiver suchz-as,for example, :the audio-output stage, 'the video zoutputistage, .or :the:vertical deflection circuit. It willqbeaunderstoodthat'the otherterminalaof the auxiliaryzload is connected tdgroundrsoaszto drawzanzadditional' current-.fromxthe: supply .2 5 through :the '':secondary'15 zand1isolating inductance I0. )Theadjustablemesistor 26 1 across"byepasscapacitor 2i operates to shunt a variable-amount.ofzcur- .rentdirectly-.toithe auxiliaryrload :circuitsandmay bemused toobtainav-arious degrees linearity-r110 .ofiset transmitted defects 1 incamerasweep line- 2arity. 1 By such an arrangement, .the additional.current :may be passed through secondary 'winding [5 without disturbingsubstantially the conditions in sscanning jyoke 3 so that 'an additionalraster 'centering means is not required during adjustment of the currentdrawn bythe auxiliary cload i-the vicinity ofideal linearity .of sweep..The reactanceiof .thet-shunt .inductance'lfl operrates-to.-isolate thealternating currentzloading'ie't- (feet of the-auxiliary load. Thus,connection of the -,auxiliary load 'to the lower end of :isolatinginductance 20 .produces least displacementofithe Taster :for the same:change in linearity of the scanning waveform.Additionalpictureinformation qcenteringreffects :may -.-be requiredtoofiset synchronizing :phase delay. or to-secure equality :of residualblanking margins. -:In:the-.event .thatelectrical centering is alreadyemployed in the receiver, the alternative circuit sshown in Fig. '2 maybe utilized. In "Fig. 2, corresponding elements have been indicated bythe same reference numerals and a'detailed description'thereofistconsideredunnecessary herein. In the -.circuit :of Fig. "2, the shunt'widthccontrol .20 .is illustrated as connected between a tap 35 tonsecondary winding l5 and one end thereof, the scanningyokefi being.connectedin serieswith a gvariable'resistorifi between tap 35 and theother end of :secondary winding 15. Variable -.resistor 26, which isinseries withthe scanning inductance .3, -.i s anelectricaL centeringcontrol and operates to vary the unidirectional component of current;flowing through "the scanning inductance 3. It will be understood that aunidirectional current flowing tthrough scanning inductance 3 produces.a' constant-deflection of the: electron beam of theeoathcdeiraytube:inadirection determined hyrfihe: polarity-pf -t'he (unidirectional current.

:E'ig; :2 the additional inure;

a. subtractive magnetizing force is supplied by an auxiliary loadcircuit which is connected to the lower end of scanning inductance 3.The auxiliary load may again comprise any power consuming circuit in thereceiver which will draw the value of current necessary to produce thedemagnetizing balancing force AH. In operation, the circuit of Fig. 1reduces the raster centering action produced by adjustment of resistor26 of Fig. 2, but similar adjustment of the circuit of Fig. 2 may beaccompanied by a change in linearity and amplitude of the scanninwaveform. However, changes in the linearity may be substantiallycompensated for by readjustment of the linearity control inductance I I.Also, changes in the amplitude of the scanning waveform may becompensated for by readjustment of width control 20. If the value ofresistor 26 is decreased, as by moving the tap thereof toward the supply25, the amplitude of the scanning waveform decreases correspondingly dueto the decreased load across that portion of the secondary winding I 5.Such a change in amplitude may be compensated for by readjustment ofwidth control inductance 20.

'- If the picture centering is set to the right, as

by raising the tap on resistor 26, the unidirectional current drawnthrough the scanning inductance 3 and secondary I5 is increased and thevalue of the width control inductance 20 in decreased to reduce theincreased amplitude of the scanning waveform.

*In either the arrangement of Fig. 1 or Fig. 2, there is employed thecirculation of a unidirectional current through the secondary windin ofthe sweep transformer so that the magnetizing force of the primary andsecondary windings is approximately balanced. With the adjustment ofcombined current excursions to secure raster centering and desired sweepwidth, relatively little effect upon the sweep linearity is experiencedin our arrangement.

It is an important feature of our invention that the efficiency of theelectromagnetic deflection circuit is substantially increased overprevious systems of this character due to the fact that the fullcapabilities of the transformer core material are realized. Thus, by ourarrangement, a sweep output transformer having a substantially reducedvolume of core material may be made to produce the same output ofelectromagnetic scanning energy as conventional sweep transformers manytimes greater in size. Also, with the advent of cathode ray tubes ofincreased sweep angle and higher rating of insulation, which requireincreased electromagnetic deflection energy and high voltage supply, ourimproved electromagnetic deflection system enables present-day circuitsto be modified so as to provide the required increase in sweep energyand anode potential without any substantial change in the elements ofthe existing system.

While our invention has been described by reference to particularembodiments thereof, it will be understood that numerous modificationsmay be made by those skilled in the art without departing from theinvention. We therefore aim in the appended claims to cover all suchequivalent variations as come within the true spirit and scope of ourinvention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. In an electromagnetic scanning circuit of the type employing a sweeptransformer having a ferromagnetic core surrounded by primary and 8 lsecondary windings and also employing power supply means for passingcontinuous unidirectional currents through said two windings whichproduce unequal opposing fluxes, whereby said transformer core tends tobe operated at a point unsymmetrically positioned on the B/H curve ofsaid core, means for increasing the linearity and efiiciency of saidtransformer comprising an auxiliary direct current load circuitconnected in series with said secondary winding, said load circuithaving a predetermined admittance value suflicient to cause anadditional component of continuous unidirectional current to flowthrough said secondary winding of proper polarity and of magnitudesufiicient to equalize said fluxes, thereby to shift the operating pointof said core substantially to the center of the B/H curve thereof. I

2. In an electromagnetic scanning circuit of the type employing a sweeptransformer having a ferromagnetic core surrounded by primary andsecondary windings and also employing power supply means for passingcontinuous unidirectional'currents through said windings so proportionedthat the magnetizing force produced by flow of current through saidprimary winding normally exceeds the magnetizing force produced by flowof current through said secondary winding by a predetermined amount,means for substantially increasing the efliciency of saidelectromagnetic scanning circuit comprising an auxiliary direct currentload circuit connected in series with said secondary winding, said loadcircuit having a predetermined admittance value selected to cause anadditional component of continuous unidirectional current to flowtherein of such magnitude that an additional magnetizing force of saidpredetermined amount is established in said secondary winding, wherebythe operating point of said transformer core is positioned substantiallyin the center of the B/H curve thereof.

3. An electromagnetic deflection circuit comprising, a sweep transformerhaving primary and secondary windings associated therewith, an electrondischarge device having an output electrode connected to one end of saidprimary winding and a cathode connected to a point of common referencepotential, means for controlling the flow of current through said deviceand said primary winding in accordance with a scanning wave of desiredwaveform, a primary load circuit including a deflecting coil connectedin circuit with said secondary winding, 3, rectifier, means includingsaid rectifier for cross connecting one end of said secondary windingand the other end of said primary winding, a source of unidirectionalpotential having one terminal connected to the other end of saidsecondary winding and the other terminal connected to said referencepoint, an inductance having one terminal connected to said one end ofsaid secondary winding, and an auxiliary load circuit connected acrosssaid source through said inductance and said secondary winding, saidauxiliary load circuit having admittance value such that the totalmagnetizing forces produced by flow of unidirectional current from saidsource through said primary and secondary windings are substantiallyequal.

4. An electromagnetic deflection circuit comprising, a sweep transformerhaving primary and secondary windings associated therewith, an electrondischarge device having an output electrode connected to one end of saidprimary winding and a cathode connected to a. point of common referencepotential, means for controlling the flow of current through said deviceand said primary winding in accordance with a scanning Wave of desiredwaveform, a primary load circuit including a deflecting coil connectedin circuit with said secondary winding, a rectifier, means includingsaid rectifier for cross connecting one end of said secondary Windingand the other end of said primary winding, a source of unidirectionalpotential having one terminal connected to the other end of saidsecondary winding and the other terminal connected to said referencepoint, and an auxiliary load circuit connected across said sourcethrough said secondary winding, and a resistance connected in circuitwith said source and said auxiliary load circuit, said auxiliary loadcircuit and said resistance having a combined admittance value such thatthe magnetizing forces produced by flow of unidirectional currentsthrough said primary and secondary windings are substantially equal.

5. An electromagnetic deflection circuit comprising, a sweep transformerhaving primary and secondary windings associated therewith, an electrondischarge device having an output electrode connected to one end of saidprimary winding and a cathode connected to a point of common referencepotential, means for controlling the flow of current through said deviceand said primary winding in accordance with a scanning wave of desiredwaveform, a primary load circuit including a deflecting coi1 connectedin circuit across said secondary winding, a rectifier, means includingsaid rectifier for cross connecting one end of said secondary windingand the other end of said primary winding, a source of unidirectionalpotential having one terminal connected to the other end of saidsecondary winding and the other terminal connected to said referencepoint, an isolating inductance having one terminal connected to said oneend of said secondary winding, an auxiliary load circuit connectedacross said source through said inductance and said secondary winding,and a shunt resistance connected between one terminal of said source andsaid load circuit, said resistance being variable, whereby fiow ofcurrent through said secondary winding to said load circuit may bevaried, said auxiliary load circuit having a, predetermined admittanceso selected that the magnetizing forces produced by flow ofunidirectional currents through said primary and secondary windings maybe substantially equalized by adjustment of said resistance.

6. An electromagnetic deflection circuit comprising, a sweep transformerhaving primary and secondary windings associated therewith, an electrondischarge device having an output electrode connected to one end of saidprimary winding and a cathode connected to a point of common referencepotential, means for controlling the flow of current through said deviceand said pri- 4 mary winding in accordance with a scanning wave ofdesired waveform, a, rectifier, means including said rectifier for crossconnecting one end of said secondary winding and the other end of saidprimary Winding, a source of unidirectional potential having oneterminal connected to the other end of said secondary winding and theother terminal connected to said reference point, a scanning inductanceconnected to said one end of said secondary winding, and a load circuitconnected across said source through said inductance and said secondarywinding, said load circuit having a predetermined admittance value suchthat the magnetizing forces produced by flow of unidirectional currentsthrough said primary and secondary windings are substantially equal.

7. An electromagnetic deflection circuit comprising, a sweep transformerhaving primary and secondary windings associated therewith, an electrondischarge device having an output electrode connected to one end of saidprimary winding and a cathode connected to a point of common referencepotential, means for controlling the flow of current through said deviceand said primary in accordance with a scanning wave of desired waveform,a rectifier, means including said rectifier for cross connecting one endof said secondary winding and the other end of said primary winding, asource of unidirectional potential having one terminal connected to theother end of said secondary winding and the other terminal connected tosaid reference point, a scanning inductance connected in circuit withsaid secondary winding, a direct current load circuit of predeterminedimpedance connected across said source through said secondary winding,and a resistance connected in circuit with said source and said loadcircuit, said resistance being variable, whereby flow of current throughsaid secondary winding to said auxiliary load circuit may be varied,said auxiliary load circuit having a predetermined admittance soselected that the magnetizing forces produced by flow of unidirectionalcurrents through said primary and secondary windings may be adjusted tobe substantially equal by adjustment of said resistance.

CHARLES E. TORSCH. JOHN B. COULLARD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,443,030 Foster June 8, 19482,460,601 Sch-ade Feb. 1, 1949 2,466,537 De Vore Apr. 5, 1949 2,474,474Friend June 28, 1949 2,478,744 Clark Aug. 9, 1949

